A comparison has been made among mechanical properties measured and plastic deformation process at different copper thickness during nanoindnetation and tensile test of the samples. Molecular dynamics simulation was used to study of mechanical properties of NiTi/Cu bilayer by nanoindentation and tensile testing. No distinct grain boundary sliding was found. While the plastic tension-compression asymmetry should mainly result from the different kinds of atomic interaction, intergranular fracture and dislocation glide. The elastic tension-compression asymmetry should be ascribed to the higher friction in compression, the asymmetry of interatomic potential, and the effect of cutoff distance in a MD simulation. Tension-compression asymmetry was observed and analyzed systematically. As the strain rate varies in the range between 5E8 and 1E9 s⁻¹, strain rate effect becomes insignificant, and the corresponding loading can be regarded as quasi static or low strain rate loading. The yield strain, yield stress and flow stress increase in power form with the increase of strain rate. The Young's modulus increases with the increase of strain rate. The Zener's familiar anisotropy index A of the polycrystalline VN model is 0.957, very closed to 1.0, demonstrating its elastic isotropy. We performed molecular dynamics (MD) uniaxial tension and compression simulations of nano-polycrystalline (npc) vanadium nitride (VN) with different strain rates to investigate strain rate effects and tension-compression asymmetry in npc VN. We also found that the strengthening/softening induced by TB depends on the deformation mechanisms induced by indenter directions. The migration of TB can be observed, which may release the internal stress, resulting in softening while the dislocation locking and pileup at TB can enhance the strength. Different deformation mechanisms can be found for inelastic deformation, such as twinning and dislocation glide. We found that the effect of the indenter orientation is insignificant in the elastic stage, but significant in the following inelastic deformation. To investigate the TB effects and the in-plane anisotropy, nanoindentations on VN (111) films with and without TB were simulated with molecular dynamics, in which a cylindrical indenter was used, and its longitudinal axis were assigned along and, respectively. However, the roles of TB on the mechanical properties and strengthening/softening of transition metal nitrides remain unclear. Twin boundaries (TBs) have been observed in and introduced into nonmetallic materials in recent years, which brought new concepts for the design of new structural materials.